1. Field of the Device
Embodiments of the present invention relate to an organic light emitting display device having pixels and a method of driving the same.
2. Description of the Related Art
Recently, various flat panel display devices capable of reducing weight and volume as compared to a cathode ray tube have been developed. These flat panel display devices include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), an organic light emitting display (OLED) device, and the like.
Among them, the organic light emitting display device, which displays an image using organic light emitting diodes that generate light by recombining electrons and holes, has a rapid response speed and can be driven at a low power.
The organic light emitting display device includes a plurality of data lines, scan lines, and a plurality of pixels arranged in the form of a matrix at crossing regions of the data lines, the scan lines, and/or the power lines. Each of the pixels generally includes an organic light emitting diode, two or more transistors including a driving transistor, and one or more capacitors.
The organic light emitting display device described above has low power consumption, whereas an amount of current flowing to the organic light emitting diode is varied according to the threshold voltage variation of the driving transistor included in each pixel, which causes non-uniformity of the display. That is, according to a production process variable of the driving transistor included in each pixel, characteristics of the driving transistor may be changed. In practice, it is impossible or very difficult that all transistors in the organic light emitting display device are manufactured in currently known process steps so as to have the same characteristics. Therefore, the threshold voltage variation of the driving transistors occurs.
In order to solve the problem described above, a method of adding a compensation circuit formed of a plurality of transistors and capacitors to each pixel has been proposed. The compensation circuit allows the driving transistor to be connected in a diode form during a scan-on time, thereby compensating for the threshold voltage variation of the driving transistors.
Recently, in order to improve image quality, a method of driving an organic light emitting display device at a high definition and/or a high driving frequency has been proposed. However, in the case in which a panel is driven at the high definition and/or the high driving frequency, a supply time of the scan signals is reduced, and as a consequence, it is impossible or very difficult to compensate for the threshold voltage of the driving transistors.